The invention resides in a process for the purification and/or treatment of communal and/or industrial waste waters particularly for use in marine facilities and an arrangement for performing such a process.
Besides community wastewater processing plants, which are installed to treat the wastewaters from relatively large areas, there are communal and/or industrial wastewater flows, which must be processed or purified locally before they can be discharged into the environment. There are generally three types of decentralized plants with which wastewaters can be purified or, respectively, treated. These are plants found, for example, in communities which are not connected to central communal wastewater treatment and purification plants (case 1). The industrial wastewater treatment for problematic compounds, which, because of unfavorable ratios, have concentrations of CSB to BSB.sub.5 (case 2), which cannot be treated in conventional purification or, respectively, treatment plants.
The wastewater treatment in marine facilities such as ships (case 3) poses a particular problem.
Especially in cases 1 and 3 wastewaters of a highly variable composition must be treated. Also, the volume flows vary widely. In case 3, additionally the conditions existing in marine facilities such as ships must be taken into consideration.
Particularly for use in marine installations, for example on board of ships, very rigid rules have been established by international organizations such as the IMO (International Maritime Organization) governing the release of contaminants from marine facilities into the sea. The limits set by these organizations are in some cases substantially lower than the limit values for the discharge of treated wastewaters from land-based stationary treatment and purification plants. Since the seas and, increasingly, sensitive water bodies such as the Arctic and the Antarctic are visited by research vessels and fishing boats and now also by passenger ships (cruise ships) very rigid rules have been established. In the past, the wastewater generated in marine installations has been collected in tanks, at least while a ship was in a harbor or in national waters and was then discharged into the sea in international waters, often without having been reliably purified. In fact, often the wastewater has been discharged without any purification or treatment so that all the waste and contaminants were released into the sea.
This is unacceptable for the reasons given above and will not be permissible in the future. On the other hand, on-board treatment of wastewaters on marine installations requires highly compact equipment because of the limited space available. In addition, the equipment must not be affected by the rolling motion of ships, that is, the treatment apparatus must remain fully operative even if the ship is not stable. Furthermore, the wastewater flows in ships are generally not separated, that is, in effect they represent a mixture of communal and industrial waste waters. Particularly with the introduction of technical solutions (grease, cleaners, tensides, disinfectants, etc.), the ratio of CSB/BSB.sub.5 increases above that common in communal wastewaters. Also, changes may be very sudden. Because of the low content of microorganisms present in conventional reaction systems with maximal bio-mass concentrations of 5 g/l, such sudden changes cannot be accommodated. As a result, the biological decomposition of the waste material is much decreased.
It is therefore the object of the present invention to provide a process and apparatus for the purification of wastewater streams, which may be subjected to highly variable hydraulic loads as they are present in marine installations such as ships. The treatment should be quasi-continuous and in a quasi-closed system and should not require any maintenance or attendance by personnel. The process and equipment should also be simple and relatively inexpensive.